Coal Seam Gas

Description:

Coal seam gas (CSG) or coal bed methane is a form of natural gas extracted from coal seams. While it is sold and used in the same way as traditional gas it's produced by non-traditional means. Over the last decades it has become an important source of natural gas for the United States and Canada. More recently Australia and Asia are experiencing an increase in CSG exploration and development.

CSG is extracted from the coal and, unlike traditional gas, contains little hydrogen sulfide. CSG is distinct from a typical conventional gas reservoir, as the gas is stored within the coal by a process called adsorption. The methane is in a near-liquid state, lining the inside of pores within the coal (called the matrix). The open fractures in the coal (called the cleats) can also contain free gas or can be saturated with water - this makes coal both a source and reservoir rock. To extract the gas the pressure in the coal bed needs to be relieved and this is done by pumping out the ground water. The large quantities of extracted water can pose an environmental hazard due to the high sodium content.

Unlike natural gas from conventional reservoirs, coal bed methane contains very little heavier hydrocarbons such as propane or butane, and no natural gas condensate. It often contains up to a few percent carbon dioxide. Coal seam reservoirs usually contain 6 - 7 times more gas than traditional reservoirs.

Coal seam gas exploration and extraction is currently experiencing a boom as gas prices rise along with demand for cleaner energy sources.

Enablers:

• 1970s OPEC oil embargo.
• Availability in nations with little or no traditional gas reserves (e.g. China, India).
• China's demand for coal and extensive coal mines.
• Coal mine safety.
• Development and dissemination of reservoir engineering and completion technology (1982 - 1987).
• Growth of natural gas based electricity generation.
• How natural gas prices.
• Methane reduction in coal mining leads to less coal mining accidents and lower greenhouse emissions.
• Price and tax incentives (US 1980 Crude Oil Windfall Profits Tax Act, Section 29)
• Private sector research (especially Amoco, now BP).
• Regulation on clean energy production.
• Rising awareness of carbon emissions.
• Rising demand for natural gas.
• Risk of nationalisation of traditional sources of natural gas.
• US public sector research (US Bureau of Mines, US Department of Energy, Gas Research Institute)

Inhibitors:

• Environmental impact of extracting coal seam gas - mainly the disposal of water.
• High initial costs.
• Lower gas rates than conventional reservoirs.
• Movement away from fossil fuels - regardless how clean - towards renewable energy sources.
• Low natural gas prices.

Paradigms:

• Brings a new view on previously uneconomical coal deposits. Previously if a coal deposit was uneconomical for mining it was left unexploited; now it is possible to extract gas from the coal bed for a much lower cost than mining.
• Changes the way China thinks about meeting energy requirements.
• Coal is now seen as a reservoir rock as well as a source rock.
• Methane emissions can be reduced profitably in coal mines.

Experts:

• [Arrow Energy]
• [ConocoPhillips]
• [Origin Energy]
• [U.S. Environmental Protection Agency]
• U.S. Geological Survey
• [Westside Corporation Limited]

Timing:

• Late 1970s - Coal seam gas exploration starts in ernest in the U.S.A.
• Mid 1980s - Established production in San Juan and Black Warrior Basins.
• 1990s - commencement of development in Australia

Web Resources:

• [Advanced Technology Group COAL BED METHANE - TECHNOLOGY STATUS]
• [Center for Energy and Global Development - Coal bed Methane: Vision for Clean Energy]
• [Energy Justice Network - Coal Bed Methane]
• [The Environmental Literacy Council]
• [Unconventional Gas Center]
• [US Geological Survey - Coalbed Methane - An Untapped Energy Resource and an Environmental Concern]
• [Wikipedia - Coalbed methane]